OF THE THIRD TANGANYIKA EXPEDITION. 19 
А few species, such as Potamogeton Livingstonei, only known from Lake 
Nyasa, Boottia scabra, previously found in the Nile and Gazelle Rivers, and 
now brought from Tanganyika, and Xyris multicaulis, a marsh-plant found 
in swampy ground at Bukoba, Victoria Nyanza, and previously known only 
from Namasi, in Nyasa-land, have a more restricted distribution. 
The only remarkable plant is a new variety of Fimbristylis stolonifera, 
deseribed by the late Mr. C. B. Clarke from swampy ground near the 
harbour, Bukoba, Victoria Nyanza ; the species has only been previously 
recorded from India and China (Yunnan). 
As shown in the accompanying table (p. 28) (in which two species of Chara 
are included), 16 species were collected at Lake Nyasa, 16 at Victoria Nyanza, 
and 27 at Lake Tanganyika. The fact that the larger number found at 
Tanganyika bears a small proportion to the much longer time spent there, 
suggests that there was not very much more to collect in the way of aquatic 
seed-plants, ferns, and Сћагасее. It is surprising, however, that the margins 
of the lakes yielded no Lemnacez, as several species of Lemna and Wolfia are 
recorded from British Central Africa ; nor Alismaces, such as Limnophyton, 
known from several localities in Nile-land and the Mozambique district. 
The characteristic tropical African water-weed Lagarosiphon is also unre- 
presented in the collection ; we may note, however, that a species, L. Nyasse, 
has previously been described from one of the lakes. Mr. Bennett remarks 
on the paucity of the number of species of Potamogeton found in the margins 
and bays of these lakes. 
A comparison of the aquatic plants (omitting the Algæ) from Lake 
Tanganyika with those from Lake Nyasa and Victoria Nyanza throws no 
light on any theory as to a difference of origin or conditions, present 
or past, in the case of Tanganyika as compared with the other two lakes. 
The true aquatics which were collected only in Tanganyika are the 
following :— 
(1) Najas marina, a cosmopolitan submerged plant which occurs in two 
of the Norfolk Broads and at other reputed brackish localities, but is 
also a common freshwater weed, occurring in the Swiss lakes, and 
plentiful generally in the lakes and rivers of the Continent of 
Europe. 
(2) Potamogeton pectinatus, also cosmopolitan and also found in both 
brackish and fresh water. The leaves are submerged. 
(3) Ottelia lancifolia, a freshwater species with both submerged and 
floating leaves; widely distributed in Tropical Africa. 
(4) Boottia scabra, a freshwater species with submerged leaves; recorded 
from the Nile and Gazelle Rivers in Central Tropical Africa, 
(9) Nymphea Lotus, a water-lily ; recorded from North and Tropical 
Africa and Madagascar. 
c2 
